This invention relates to genetically engineered DNA enabling organisms, particularly bacteria, to produce, process, and secrete desired mature proteins, particularly chitinase. The invention also relates to the use of such microorganisms for controlling pests that are sensitive to chitinase. The term "engineered" or "engineered DNA" means a DNA that has been modified by human intervention, e.g. by genetic engineering techniques.
Various organisms actively secrete enzymes that digest chitin, a complex carbohydrate found in insect cuticles and shellfish shells, comprising a polymer of N-acetylglucosamine monomer units. Chitinase has been proposed for use in a variety of applications, for example as a pesticide to combat pests such as fungi, nematodes, and insects. Fuchs et al., Applied and Environ. Microbiol. 51(3):504-509 (1986) propose enzymatic digestion or deformation of the chitin component of pests such as insects, fungi, and nematodes, to control those pests. They propose to produce and deliver chitinase to the site of infestation by appropriate rhizoplane-or phyloplane-colonizing bacteria such as fluorescent Pseudomonads.
Chitinase also can be used to process industrial waste, e.g., shellfish shells.
Chitinase genes of Serratia marcescens have been cloned. For example, Fuchs et al., cited above, report that S. marcescens produces five unique chitinolytic proteins, with subunit molecular masses of 21, 36, 48, 52, and 57 kilodaltons. A gene producing one of these proteins (the 57 kilodalton protein) was cloned and expressed in Escherichia coli and in Pseudomonas fluorescens. Suslow and Jones EP 0157351 disclose cloning of two independent chitinase genes from S. marcescens. Jaworski et al. EP 0171381 disclose cloning a chitinase gene from S. marcescens, and expression of the gene from a strong constitutive promoter in P. fluorescens to inhibit nematode infection of soybeans.